The 30-year-old, who has 19 grand tour stage wins to his name, including 14 at the Tour de France, joined the outfit last year but never managed to reproduce the form that made him one of the world's best sprinters.
"At this moment, I am not able to train and race at the highest level," Kittel said in a statement which also thanked his team for all its support.
"For this reason, I have decided to take a break and take time for myself, think about my goals and make a plan for my future."
"It was for me a long decision process where I raised a lot of question about how and where I want to go as a person and athlete and what is really important to me.
"I love cycling and my passion for this beautiful sport is never gone but I also know what it requires from me and what I need to be successful."
Earlier this year, Kittel spoke to journalist Sophie Smith about his difficult transition from experiencing numerous victories to just a handful for her Procycling Magazine piece on the peloton's mental health.
"You know, after 2018 I learned again what a business it is that we are in. It's not a sport in the first place, it's a business, and that's something you don't really realise as a neo-pro.
"It really is a lot of expectation from other people. If you're performing well everyone is happy, and if everything is not going to plan then not everyone is happy. That's something you have to learn to deal with.
"A lot of it was black in 2018. I don't have to hide that it goes very quick that you feel that you're on your own and then it's hard to see the reasons why you're actually doing this."